1. Field of the Invention
The present invention is directed to aircraft, and more particularly to a reduced visibility single wing rotorcraft.
2. Description of the Related Art
A rotorcraft (i.e., an aircraft that is kept partially or completely airborne by airfoils rotating around a vertical axis) has several advantages over conventional airplanes. A rotorcraft can take off and land nearly vertically, without requiring a large runway or landing strip. A rotorcraft can move relatively slowly, compared to the speeds required to maintain flight for an airplane, and can even hover in place. Furthermore, a rotorcraft may have an increased resistance to turbulent wind conditions, due to the potentially large angular momentum of the spinning airfoils or wings.
A helicopter, the most common rotorcraft, has all of the advantages described above, but it is generally a complex and expensive machine, requiring an elaborate control system to ensure that it remains stable as it flies. Typically, the control system for a helicopter controls the pitch (nose up, tail down for positive pitch), roll (left up, right down for positive roll), yaw (nose right, tail left for positive yaw), and altitude.
An improvement over the helicopter is disclosed by Shoulders in U.S. Pat. No. 3,915,414, which describes an aircraft configured as a pod from which a single wing extends. As it flies, the entire aircraft rotates within an air mass to produce lift with the wing (as opposed to a helicopter, which has a non-rotating portion to carry an operator and a payload). The rotation is obtained by jet flow from the trailing edge of the wing adjacent to its tip. A separately rotating impeller within the pod provides the jet flow. The impeller also acts by centrifugal force to normally set a pitch plane for the wing of the craft. A detector interacts with the magnetic field of the earth and generates a signal that is indicative of the angular orientation of the aircraft at any time. A synchronous sensing and remote control system takes into account the angular orientation in operating a control flap positioned in the jet stream as desired to change the plane of rotation and, hence, the direction of translation of the rotating aircraft.
Despite the improvements of Shoulders's device over a conventional helicopter, principally as a reduction in complexity and cost, there are still several drawbacks. The control flap is a moving part that must be engaged and disengaged at the proper points in each rotation cycle as the device flies, and is subject to wear and failure. In addition, the engine is a two-cycle engine that uses a liquid fuel, and must be carefully designed and installed to function properly in the rapidly rotating environment of a rotorcraft. Finally, because a large amount of the device's mass is located in close proximity to the center of mass, the rotational inertia (or moment of inertia) is relatively small.
Furthermore, the device of Shoulders is readily visible (as is the case with most aircraft). If the aircraft of Shoulders were used as a surveillance device, its visibility would be a potential drawback.
Accordingly, there exists a need for a further simplified rotorcraft, which does not rely on a moving part for control that is specifically engaged and disengaged at the proper points in each rotation cycle, does not use a liquid fuel-powered engine, has improved stability during operation due to an increased rotational inertia, and is substantially invisible.